A cooling mechanism of a plurality of circuit boards (printed boards) is disclosed in, for example, Japanese Patent Laid-open Application No. 2011-249731.
According to the cooling mechanism, the circuit board is arranged in parallel with a flow path of a cooling wind for efficiently cooling the circuit board. In a case where a connection board (back-plane) for coupling the circuit board is arranged orthogonally to the flow path (for example, FIG. 2), the connection board closes the flow path of the cooling wind, and there is a concern of preventing the circuit board from being cooled. Consequently, a wind opening is provided at the connection board.